Insulin-induced hypoglycemia to 2.5 mM (45 mg/dl) increased P300 latency and prolonged reaction time in IDDM patients, indicating a cognitive dysfunction threshold between 2.5 and 3.5 mM.
What is the hypoglycemic threshold for cognitive dysfunction in poorly controlled IDDM patients?
In poorly controlled IDDM patients, the hypoglycemic threshold for cognitive dysfunction is between 2.5 and 3.5 mM, similar to healthy controls, with cognitive recovery lagging behind the restoration of euglycemia.
Fourteen poorly controlled insulin-dependent diabetes mellitus (IDDM) patients (HbA1c 11 ± 0.5%) with a mean ± SE duration of disease of 15 ± 2 yr were studied to evaluate the hypoglycemic threshold for cognitive dysfunction under insulin-induced hypoglycemia. The P300 event-related potential, a measure of cognitive function, and reaction time (RT) in response to visual stimuli under euglycemic conditions and at plasma glucose concentrations of 3.5 and 2.5 mM (63 and 45 mg/dl, respectively) during a constant insulin infusion were recorded. Baseline P300 latency was similar to that of a nondiabetic control group, but baseline RT was greater in the IDDM group. There was no increase in P300 latency or RT under euglycemic clamp conditions or at a plasma glucose level of 3.5 mM (63 mg/dl). However, when plasma glucose was lowered to 2.5 mM (45 mg/dl), there was an increase in P300 latency and a prolongation of RT. As plasma glucose returned to baseline, P300 latency and RT remained prolonged. After administration of intravenous glucose and a meal, P300 latency and RT returned to baseline. P140, an event-related potential reflecting sensory processes, was not altered. Because P300 latency changes paralleled RT changes, hypoglycemia appears to slow decision-making processes in IDDM. This study revealed that 1) baseline P300 latency is not elevated in poorly controlled IDDM patients, suggesting no cumulative cognitive dysfunction; 2) the hypoglycemic thresholds for cognitive dysfunction in poorly controlled IDDM are between 2.5 and 3.5 mM (45 and 63 mg/dl, respectively)and are similar to those found in control subjects, suggesting no maladaptive CNS response to hypoglycemia; 3) recovery of cerebral dysfunction, as judged by alterations in P300 latency and RT, lagsbehind the disappearance of hypoglycemia; and 4) there is individual variability to the adverse effects of hypoglycemia on cerebral function.
Blackman et al. (Sun,) conducted a other in Poorly controlled insulin-dependent diabetes mellitus (IDDM) (n=14). Insulin-induced hypoglycemia vs. Euglycemic conditions and nondiabetic control group was evaluated on Cognitive dysfunction measured by P300 event-related potential latency and reaction time (RT). Insulin-induced hypoglycemia to 2.5 mM (45 mg/dl) increased P300 latency and prolonged reaction time in IDDM patients, indicating a cognitive dysfunction threshold between 2.5 and 3.5 mM.